I am now on plasma 6 and had no problems with the upgrade as after having had problems in the past I now only use breeze. Everything is default.
But I have just noticed that on pressing ctrl-w and going into the overview, I no longer have the small desktop selection windows that I should have, and that I had on plasma 5.
Yes, the Overview code was rewritten, and it will now only include the virtual desktops if they are all arranged in one row or in one column. If you have your virtual desktops arranged in multiple rows and/or multiple columns — or otherwise put, a grid — then they will no longer be included in the Overview.
The inclusion of the desktops in the Overview if they are arranged in a grid has already been filed as a feature request with the KDE developers upstream, so we’ll have to wait for any changes in that regard.
The good news however is that you can easily bring up the desktop grid by pressing Meta+G.
Thank you so much for your reply, and I am glad I asked the question, as I was thinking of neuking my entire home folder in an attempt to fix this, and it would not have made any difference.
My desktops are arranged in a grid, as I use 6 of them.
Meta and g will do for now I suppose. Thanks again.